GASES

The invention relates to a method for plasma - electrochemical purification of flue gases, applicable in any device for recovery and oxidative cleaning of flue gases from ash particles and from the oxides of carbon, sulfur and nitrogen.

BACKGROUND OF THE INVENTION

Method and apparatus /BG51440 from 24.08.1990/ are known, according to which air, flue gases and similar gas mixtures pass through a space where one or more discharge electrodes emit electrons; when the electrons fall on the surface of the solid particles they ionize them, as a result the particles are caught on the anode, where they are deposited and from where they are washed with water. By this method it is impossible the molecules of harmful gases to be excited, broken up or ionized in order to be transformed into elementary particles or into harmless compounds.

In patent CN101920167A from 22.12.2012 the technology is described for capturing sulfur dioxide at low concentrations using the process of electroosmosis, implemented in a three-chamber apparatus for ultrasonification, serving for cleaning the perforations of the applied for separation membranes. Membranes with fine perforation are used and the holes can not be cleansed effectively even by ultrasonification. Furthermore, electroosmosis can not compete with the technology of electrochemical gas cleaning from harmful gas components in performance, efficiency and simplicity of equipment.

A technology is known for complex flue gas cleaning from harmful contaminants in a single reactor (Euro-Asian patent 005264 from 30.12.2004). The technology is based on the principles of plasma electrochemistry, namely that at the passage of gas flow through area of electrons emitted by needle cathode, directed towards the anode, the electrons having sufficient energy excite and break up the molecules of harmful gas components and the contained in the gas water vapor into ions and radicals. The result is that the ash particles are negatively charged and as in the electrical filters, they are captured by the anode, while the particles of sulfur and carbon after charge formation recover and after falling on the anode with the ash particles they are taken out of the reaction zone by the water layer moving on the surface of the anode, which is inclined as to ensure smooth flow of the water with the captured components The cathode is also inclined accordingly in order to be parallel to the anode for providing uniform electric gradient along the whole length of the reaction zone. According to the described patent the flue gas moves transversely to the electron flow and the direction of its motion is from top to bottom or vice versa.

In European patent 200800310A1 from 29.12.2007 a method is described for cleaning flue gases from their harmful gas components which is not substantially different from the method described in Euro-Asian patent 005264. The difference is only in the apparatus for implementation of the method, which is cylindrical in shape and here the movement of the electron flow and gases is not unidirectional as well.

SUMMARY OF THE INVENTION

The objective of the invention is to improve the efficiency of cleaning of flue gases from various boiler installations by modifying the aerodynamics of the course of the process in plasma electrochemical decontamination devices.

To achieve this objective a method is created for plasma electrochemical flue gas cleaning from harmful contaminants in gas-air dynamic environment by generating a broad-range acoustic emission in the cathode-anode reaction zone and the flue gas flow, which may also contain water vapor, is supplied and directed into the reaction zone parallel to the electron flow. The gas flow and the electron flow move parallelly in the reaction zone to the approach of the landing area of the products formed. The gas flow is diverted upon reaching the anode, where the fine sulfur and carbon particles are captured by the flowing water layer With the method according to the present invention factors are provided intensifying the process of gas cleaning, which facilitate the cleansing of the emitting electronic needles from the accumulated reaction products thereon, create conditions in the reaction zone for consolidation of the fine particles of the newly formed substances, which reduces their removal by the outgoing gases and makes their retaining by the anode easier.

These factors are:

- Gas flow feed parallel to the electron flow. In this case the gas simply "washes" the body and the edge of the needles and throws away the accumulations to the anode and as these deposits are recovered elements, reduces the loss of useful substances. The disposal of deposits removes the shield on the edges of the needles and they continue to function as intended, which contributes to the high efficiency of cleaning.

- When processing gases with low water vapor content, useful in the process of cleaning, they can also be fed in parallel to the electron flow in the reaction zone. The usefulness of the water vapor is in the fact that in the reaction zone it forms restored, i.e. atomic hydrogen, which is very reactive and is given the name "nascent" hydrogen, i.e. highly reactive.

- Broad-range acoustic emission is generated with parameters from 20 to 30 000 Hz in the reaction zone together with parallel gas feed, wherein the formed fine particles of carbon and sulfur consolidate, reach the anode easier and are captured by the water layer. The usefulness of the acoustic emission is in the creation of standing acoustic waves in whose nodes the particles accumulate and consolidate.

With the method according to the present invention the following existing difficulties are overcome:

^• The difficult cleansing of needles and especially of their tips due to the fact that the gas stream, moving perpendicularly to the needles, pressures on the accumulations thereon and actually even strengthens the connection between the accumulations and the bodies of the needles, while deposits on the back of the needles do not undergo cleansing action at all, as they are screened by the bodies of the needles. • The potential losses of the elements sulfur and carbon, as they are very small in size and therefore easily deviated from their movement to the anode and taken out by the outgoing stream. This is particularly true for the particles present in the central part of the reaction zone, because the speeds of the elementary flows there are much greater than the speed of the gas along the anode.

EXAMPLE 1

Figure 1 illustrates the method according to the invention, wherein the electron flow 2 is moving parallelly to a gas flow 3, formed as a result of the perforation in the cathode. The gas is diverted towards the exit upon reaching the anode, where the velocity gradients are small and the particles, which have accumulated kinetic energy due to the fact that the gas in its movement has accelerated them, when reaching the aqueous layer 1 overcome more readily the surface tension of water and are retained therein.

The principles of the invention are elucidated by the drawings of the accompanying Figure 1, illustrating the known situation of flue gas feed across the electron flow emitted from the cathode and the innovation here proposed of electron flow 2 moving parallelly to the gas flow 3 .

Figure 1

Cross sections of segments of the reaction zone

a) Known movement of flows b) Movement of flows according to the invention